A solar battery is an apparatus for generating an electric energy by absorbing light (including sun light) and converting an optical energy of the light to an electric energy.
FIG. 1 is a diagram illustrating a basic structure of a general solar battery cell.
Referring to FIG. 1, the solar battery cell includes a positive electrode glass substrate 110 coated with a positive electrode 112, a negative electrode glass substrate 120 coated with a negative electrode 122, a catalyst layer 114 applied on the positive electrode 112 with a thin thickness corresponding to a level of an atomic layer thin film, a TiO2 layer 124 attached to a lower surface of the negative electrode 122 with a dye absorbed thereto, and sealants 140 for sealing an electrolyte 130 between the positive electrode 112 and the negative electrode 122 while maintaining an interval between the positive electrode 112 and the negative electrode 122 so as to prevent the positive electrode 112 and the negative electrode 122 from coming into contact with each other.
A voltage of an electric energy generated by one solar battery cell is generally about 1.0 V, so that, in order to generate a voltage and a current in a practical level, multiple solar battery cells are connected in series so as to increase the voltage.
A dye sensitized solar battery is formed by configuring solar battery sub modules connected in series by integrating a plurality of dye sensitized unit solar battery cells on one glass substrate and then connecting the solar battery sub modules to each other in series or in parallel. The dye sensitized solar battery may include a frame and a protection cover serving a protection function and a support function depending on a necessity.
FIG. 2 is a diagram illustrating a general structure of a solar battery sub module integrated on a single substrate.
Referring to FIG. 2, the negative electrode 122 of the solar battery cell is connected to the positive electrode 112 of the adjacent solar battery cell through partition walls 150 functioning as both a sealant and an electrical insulation between the solar battery cells, so as to form an electrically series-connected circuit. The plurality of solar battery cells is integrated, to form one solar battery sub module.
FIG. 3 is a diagram illustrating a method of manufacturing the dye sensitized solar battery by connecting the plurality of solar battery sub modules to each other.
Referring to FIG. 3, the positive electrode glass substrate 110 and the negative electrode glass substrate 120 protrude from both ends of the solar battery sub module, and the positive electrode 112 and the negative electrode 122 are coated on an upper surface of the protruding positive electrode glass substrate 110 and the lower surface of the protruding negative electrode glass substrate 120, respectively.
The protruding positive electrode 112 and the protruding negative electrode 122 are connected while overlapping each other, and the protruding positive electrode 112 and the protruding negative electrode 122 are coupled by using a conductive adhesive 310 in order to improve the electrical characteristic. In this case, the connection of the necessary number of solar battery sub modules in series is referred to as a string, and the dye sensitized solar battery is manufactured by connecting the necessary number of strings in parallel.
FIG. 4 is a diagram illustrating a method generally used in the electrical connection between the solar battery sub modules.
Referring to FIG. 4, one end of a metal tape 410 is connected to one end of the protruding negative electrode 122 of the solar battery sub module by a means, such as a soldering, and the other end of the metal tape 410 is connected to the protruding positive electrode 112 of the solar battery sub module to be connected, so as to form the electrical series-connection.
According to the existing method, there are advantages in that the electrical connection may be possible through only a simple manual operation, and a used material is relatively cheap.
However, the conventional method of electrically connecting the solar battery sub modules has low location accuracy between the solar battery sub modules which are connected to each other, so that an error of an appearance of the dye sensitized solar battery is increased, it is difficult to secure strength and durability of a connection part, so that an additional supporting structure needs to be used, and the respective solar battery sub modules are separately soldered, so that quality uniformity is deteriorated and the method is not appropriate for mass production through an automation.
As a method of solving the problems, as illustrated in FIG. 3, if the electrodes of the solar battery sub module are bonded to each other by using the conductive adhesive 310 having excellent electrical conductivity and excellent durability and mechanical strength, the dye sensitized solar battery having excellent performance and high reliability may be manufactured.
That is, when the conductive adhesive 310 are applied on the electrodes of the solar battery sub module so as to couple the electrodes to each other, and then conductive adhesive 310 is hardened in a state where the electrodes of the solar battery sub module are fixed so as not to move, the connection part is mechanically fixed and simultaneously electrically connected.
Although there are several kinds of conductive adhesives 310, when low resistance loss and high reliability for a long term are demanded like the electrode connection of the solar battery sub module, an epoxy resin-based metal paste is mainly used.
The metal paste is generally hardened at a high temperature. The metal paste is a non-conductor or has a high resistance value before the metal paste hardens, but represents a very low resistance value and has a characteristic of excellent mechanical strength and durability after the metal paste is hardened.
In the meantime, since the dye sensitized solar battery includes a liquid electrolyte, the performance of the dye sensitized solar battery may be deteriorated or destroyed when the dye sensitized solar battery is in a high-temperature state. Accordingly, a selective heating of only a corresponding region is needed in a process of heating the electrode part at a high temperature for the hardening of the metal paste in order to prevent the dye sensitized solar battery from being damaged. The local heating method may use a laser heating method, a high frequency induction heating method, and a resistive heating method, and in order to prevent a temperature increase due to heat conduction, a local cooling may be used together depending on the necessity.
FIG. 5 is a diagram illustrating a method of heating the conductive adhesive by using the resistive heating method.
Referring to FIG. 5, a heating wire 510 is laid on the electrode 112 of the solar battery sub module, and the conductive adhesive 310 is applied in a thickness equal to or larger than that of the heating wire 510. The electrode 122 of the solar battery sub module desired to be connected overlaps the conductive adhesive 310. Then, when a current flows in the heating wire 510 so as to generate heat, the conductive adhesive 310 is heated and hardened, so that the solar battery sub modules are fixed to each other. In this case, in order to prevent the temperature increase by the heat conduction, the local cooling may also be used together depending on the necessity. Further, instead of the metal heating wire, a heating wire in a form of a thin film may be attached to and formed in the electrode for use.
However, when the separate heating wire is used as described above, a thickness of the region to which the electrode is attached cannot be smaller than that of the used heating wire and a separate heating wire or a heating wire deposition process and a material are required.
Since the electrode of the solar battery sub module is a thin film having conductivity, the electrode may be heated by making a current directly flow in the electrode. However, when a high current is applied so as to heat the electrode up to a hardening temperature of the conductive adhesive, the electrode in the form of the thin film may be damaged, and an excessively wide area, as well as the region coated with the conductive adhesive, may be heated depending on a type of the electrode.